Unfortunately, my two cats get into everything. I have all my plants up very, very high lol. Not so pretty. My most adventurous cat tried to eat a cactus as well - spines & all. I've been thinking about simply using crypts, swords, etc both in and above the tank - but I can't find toxicity reports for animals on crypts. I was thinking about trailing pennywort up extended driftwood too since I use it as a floater in my tanks.

Here is more detailed info on oxalates, you can understand why I don't want to take a chance. If age means anything, my cats are 13 and might not handle things as well as they did when young;To get a bit technical, these plants contain cells known as idioblasts. Idioblasts contain raphides, which are slender, spearlike parts of calcium oxalate crystals. Raphides are sharp and needle-shaped, and are packed in a gelatinous substance. When the tip of the idioblast is broken, sap from the plant—or saliva from an animal—enters the cell, causing the gelatin to swell. The swelling action forces the raphides to shoot from the cell, kind of like a gun discharging a bullet. The calcium oxalate crystals penetrate an animal’s oral mucosa, tongue, and throat, causing damage. The cells may continue to expel crystals for a significant amount of time, even after a piece of plant material is swallowed. As this is happening, proteolytic enzymes stimulate the release of kinins and histamines by the body. The rapid inflammatory response from the release of these substances aggravates the damage caused by the crystals. Chewing, bruising, tearing, or otherwise damaging the plant is necessary to produce these effects.